Field of the Invention
The invention relates to chimeric proteins and insecticidal compositions.
Related Art
Two naturally occurring mosquitocidal bacilli, Bacillus thuringiensis subsp. israelensis (Bti) and Lysinibacillus sphaericus (Ls), are the active ingredients of commercial larvicides used for controlling nuisance and vector mosquitoes. Bti's high insecticidal activity is due to synergistic interactions among its four major proteins (Cry4Aa, Cry4Ba, Cry11Aa, and Cyt1Aa), whereas Ls's principal toxicity is caused by the binary mosquitocidal crystal, Bin, containing BinA, a toxin domain, and BinB a midgut-binding domain. Although used in many countries for over three decades, resistance to Bti is very rare. However, Bin resistance levels greater than 20,000-fold have occurred where Ls has been used intensively for mosquito control. Bti's Cyt1Aa is a lipophilic protein of low toxicity that binds to midgut microvilli causing lesions that allow other molecules to enter midgut epithelial cells. In previous studies it was shown that Cyt1Aa delays the evolution of resistance to Bti Cry proteins and Ls Bin, and can overcome resistance to these when selected for in the laboratory.